German Patent Publication DE 3,824,371 A1 (Aqua Signal AG), published on Sep. 14, 1989, discloses an illuminating device particularly for ships and aircraft. Lighting fixtures of the known system are connected through fiber optical conductors, through an optical system, and through a filter to a high power point light source which in turn is connected through electrical conductors to a power source such as the onboard electrical power supply. The filter eliminates from the spectrum emitted by the high power light source those wave lengths that do not contribute to the visible light spectrum, whereby only visible light enters into the fiber optical cable. The known system aims at reducing maintenance work on external signal lights in aircraft and ships. All lamps supplied by the same light source are switched on or off in unison by controlling the central light source.
U.S. Pat. No. 3,536,908 (Oster), issued on Oct. 27, 1907, discloses a fiber optic lighting system with bundles of fiber optical conductors which may have different lengths to feed light to individual reflectors forming light outputs. Each light output has a convex reflector held in a concave reflector. A transparent rotatable disc having sectors of different colors is positioned so that the sectors can be rotated into a light path from the light source to the inlets of the optical fiber conductor bundles. The disc is rotatable by a motor. The Oster system is especially suitable as an ornamental lighting system for trees or for display presentations. Again, all light ouputs are only switchable in unison.
The prior art discussed above does not address the problem of providing an efficient illumination for individual passenger seats to increase the passenger comfort, for example, in an aircraft passenger cabin. Conventionally, each passenger seat is illuminated by a lighting fixture including an incandescent bulb and a respective lens system installed overhead, whereby the passenger can operate a switch to activate or deactivate the individual seat or reading lamp. Some conventional incandescent bulb reading lamps with a reflector are position adjustable so that the passenger can direct the light beam to a desired area.
Conventional passenger reading lamps with incandescent bulbs have several disadvantages. Generally the incandescent bulbs require a voltage different from that of the onboard power supply network so that at least one transformer or many smaller transformers are required, generally one for each lamp unit. The total number of transformers adds to the weight of the lighting system. Further, the efficiency of incandescent light bulbs is low and unsatisfactory even if halogen lamps are used. Moreover, the exchange of defective incandescent bulbs involves a substantial maintenance effort and expense. Additionally, lighting fixtures with incandescent bulbs require a substantial space above the passenger seat. Thus, there is room for improvement.